Nitrogen availability and nitrate leaching from organo-mineral fertilizers

Abstract

Greenhouse, field and laboratory studies were conducted to determine if N availability to corn (Zea mays L.) and NO 3 leaching were affected by encapsulating conventional granular fertilizer within peat pellets (organo-mineral fertilizers or OMF). In the greenhouse, total N uptake by three 6-wk crops of corn from soil fertilized with NH 4 NO 3 was 9.1% higher than the mean from soils fertilized with OMF made with urea (OMF-urea) or with NH 4 NO 3 (OMF-AN). Total N uptake was 5.1% higher from soils fertilized with OMF-AN than OMF-urea. Differences in total N uptake among the fertilizers were constant across crops. In two field trials, total N uptake was slightly higher (4%) from soil fertilized with commercial NH 4 NO 3 than with OMF-AN. In a laboratory experiment, NO 3 from commercial NH 4 NO 3 fertilizer leached more readily from soil than NO 3 from OMF-AN. Approximately 95% of the NO 3 from commercial NH 4 NO 3 fertilizer leached from 3-cm soil cores in the first 50 mL of leachate whereas only 26% of the NO 3 contained in OMF-AN leached. In another trial, NO 3 from commercial NH 4 NO 3 fertilizer leached more deeply than NO 3 from OMF-AN after application of 2.5 cm irrigation water to soil in 63-cm leaching columns. Virtually no NO 3 was retained within the OMF-AN pellet after leaching, suggesting that the retention of NO 3 by OMF-AN used in our work is of limited duration. The OMF is an effective source of N to crops and is less prone to NO 3 leaching losses than commercial NH 4 NO 3 fertilizer when rain occurs soon after application. More work is required to determine the effect of pellet size and composition on NO 3 retention, NO 3 leaching losses and crop availability of N. Key words: Nitrate leaching, corn, organo-mineral fertilizers